Horizontal directional drilling in wells

ABSTRACT

A method and apparatus for horizontally drilling in wells utilizing a shoe assembly at the down hole end of upset tubing. The shoe assembly includes a fixed section and a rotatable section suspended below the fixed section. An electric motor and associated batteries and a gyroscope carried on the rotatable section enable an operator on the surface to selectively rotate and position the rotatable section to any desired angular location for drilling a hole in the well casing. After one or more holes have been cut in the casing, a drill assembly can be removed from the upset tubing and be replaced by a high pressure blaster nozzle to bore into the formation zones. The gyroscope enables the operator to accurately position the rotatable section to the same locations at which the holes have been cut. The drill assembly includes an electric motor with an associated battery, flexible drive shaft, and a hole saw.

This application claims the priority of U.S. Provisional PatentApplication No. 60/182,932, filed Feb. 16, 2000, and U.S. ProvisionalPatent Application No. 60/199,212, filed Apr. 24, 2000.

BACKGROUND OF INVENTION

The invention relates to not only new wells, but also to revitalizingpreexisting vertical and horizontal oil and gas vertical wells that havebeen depleted or are no longer profitable, by improving the porositiesof the wells' payzone formations. This is accomplished by providing amicro channel through the already existing casing, and out into theformation.

PRIOR ART

After a well has been drilled, completed, and brought on-line forproduction, it may produce oil and gas for an unknown period of time. Itwill continue to produce hydrocarbons, until the production drops belowa limit that proves to be no longer profitable to continue producing, orit may stop producing altogether. When this happens, the well is eitherabandoned or stimulated in a proven and acceptable process. Two of theseprocesses are called Acidizing and Fracturizing. Acidizing uses an acidto eat away a channel in the formation thus allowing the hydrocarbons aneasier access back to the well bore. Fracturizing uses hydraulicpressure to actually crack and split the formation along preexistingcracks in the formation. Both of these methods increase the formation'sporosity by producing channels into the formation allowing thehydrocarbons to flow easier towards the annulus of the well whichincreases the production of the well along with it's value. However, thesuccess of these operations is highly speculative. In some wells, it mayincrease the production rate of a well many times over that of it'sprevious record, but in others, they may kill the well forever. In thelatter case the well must be plugged and abandoned. Both Acidizing andFracturizing are very expensive. Both require dedicated heavy mobileequipment, such as pump trucks, water trucks, holding tanks, cranesalong with a large crew of specialized personnel to operate theequipment.

A more efficient method of stimulating a vertical well is to drill ahole in the well casing, and then bore a micro-horizontal channel intothe payzone using a high pressure water jet to produce a channel for thehydrocarbons to follow back to the well bore's annulus. Once an initiallateral hole through the already existing casing, has been produced. Themicro drill must be brought back to the surface. Then a high pressurewater jet nozzle is lowered into the well and through theabove-mentioned hole in the casing and out into the payzone. It thenproduces a finite lengthened channel out radially away from the wellbore into the payzone. Once this is completed, it to must be broughtback to the surface.

Because of the limitations of the present technology, the entire drillstring is then manually rotated from the surface to blindly rotate thedrill shoe (located at the bottom of the drill string) for the nextdrilling and boring operation. The process is repeated until the desirednumber of holes/bores has been reached.

It is very difficult and imperfect to rotate an entire drill string, sothat the exit hole of the shoe, which is located at the bottom of thedrill string, is pointing exactly in the desired direction. For example,if the well casing is tilted or off-line, the drill string may bind sothat the top portion rotates while the bottom portion (including theshoe) may not actually move or move less than the rotation at thesurface. This is due to the fact that all of the applied torque does notreach completely to the bottom of the drill string due to frictionencountered up hole from the shoe.

SUMMARY OF THE INVENTION

The invention provides a method and apparatus that allows the for thedrilling and completion of a plurality of lateral holes in the wellcasing in one step, removal of the drill, then lowering of the blastingnozzle and re-entering each of the holes in succession to horizontallybore into the formation without interruptions or without having to turnthe entire drill string at the surface to realign with each hole.

In accordance with the invention, the shoe assembly consists of a fixedsection and a rotating working section. The fixed section is threadedinto the down hole end of upset tubing, such as straight tubing orcoiled tubing or any other method known in the art, to lower the entireshoe assembly to a desired depth. The fixed section provides a centralchannel or passage to allow a drill apparatus (with a flexible drillshaft and a special cutting tool) to be inserted into the assembly.

The rotatable working section is attached to the fixed section by aspecially designed guide housing and ring gear that facilitates theturning of the turns the rotating section within the well casing. Thering gear converts the rotation of a motor driven transfer bar or driveshaft, turned by a self contained bi-directional variable speed DCmotor, into rotation of this section. The DC motor is controlled by anoperator at the surface and is powered by a self-contained lithiumbattery. The rotating section has a rotating vertical bore that passesthrough the center of the ring gear and into an elbow-shaped channelthat changes the direction of the of the flexible shaft and cutter froma vertical entry into a horizontal exit to allow the drilling of holesin the well casing.

A gyroscope in the rotatable section communicates the precise angularposition of the rotatable section to the operator on the surface via amulticonductor cable or by wireless transmission to allow the operatorto align the rotating section to the desired position to cut the hole.The operator can then reorient the rotatable section of the shoeassembly for sequential drilling operations, if desired. When the drillis retracted and the water jet nozzle is then lowered back through theshoe, the operator again reorients the shoe assembly.

The drill apparatus, comprised of a housing, a shaft and a bit, may beof any type desired that will fit inside the upset tubing and throughthe shoe. The bit preferably is a hole cutter comprised of a hollowcylindrical body with a solid base at one end and a series of cutters orteeth at the other end. The terminal end of the body is serrated orotherwise provided with a cutting edge or edges. As the serrated edge ofthe cutter contacts the inside of the well casing, it begins to form acircular groove into the casing. As pressure is applied, the groovedeepens until a disc (coupon) is cut out of the casing.

Sensors can be installed in the shoe assembly so that lights or alarmingdevices, on the operator's console located at the surface can indicate avariety of information:

-   -   a. The drill has entered the-shoe and is seated correctly.    -   b. The bit has cut through the casing and the hole is completed.

A core can be substituted for the hole cutter that would allow for theside of the casing and part of the formation to be cored. The corescould be brought to the surface to show the condition of the casing andthe thickness of the cement. A mill can be substituted for the cutter toallow the casing to be cut in two if the casing was damaged. The use ofa cutter and motor can be replaced with a series or battery of smallshaped charges to produce the holes in the side of the casing. If thewell bore is filled with liquid, the shoe can be modified to accept acommercial sonar device. This creates a system that can be rotated afull 360 degrees to reflect interior defects or imperfections. If thewell bore is devoid of liquids, the shoe can be modified to accept asealed video camera. This creates a system to provide a 360 degree viewof all interior defects and imperfections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of apparatus constructed inaccordance with the invention and positioned in a deep well casing;

FIGS. 2A through 2E are cross-sectional views of the apparatus on asomewhat enlarged scale corresponding to the bracketed areas shown inFIG. 1;

FIG. 3 is a transverse cross-sectional view of the apparatus taken inthe plane 3-3 indicated in FIG. 2A;

FIG. 4 is a transverse cross-sectional view of the apparatus taken inthe plane 4-4 indicated in FIG. 2B; and

FIG. 5 is a vertical cross-sectional view of a modified form of certainparts of the apparatus.

DESCRIPTION OF PREFERRED EMBODIMENT

The entire contents of U.S. Provisional Patent Application No.60/182,932, filed Feb. 16, 2000 and U.S. Provisional Patent ApplicationNo. 60/199,212, filed Apr. 24, 2000 are incorporated herein byreference.

FIG. 1 and FIGS. 2A through 2E schematically illustrate components of acylindrical shoe assembly 5 capable of horizontally drilling intovertical well casings 20 and boring into hydrocarbon payzones in oil andgas wells. It will be understood that the invention has otherapplications from the following description, such as employing a coringbit that would core into the side of the well casing 20 and part of thesurrounding formation to determine the casing condition and thecomposition of the surrounding formation, using a milling tool to cutthe well casing 20 in two, employing a series or battery of small shapedcharges to produce holes in the side of the casing 20 or to use a videocamera or sonar device to locate and determine interior defects andimperfections in the well casing 20.

The cylindrical shoe assembly 5 is composed of a fixed section 10, belowwhich a rotatable working section 11 is attached.

The fixed section 10 is threaded into the down hole end 51 of upsettubing 52, or straight tubing or coiled tubing. The upset tubing 52enables the shoe assembly 5 to be lowered to a desired depth within thewell casing 20. The fixed section 10 has a central channel or passage 53to allow for the insertion and retraction of a drill apparatus 12 thatis comprised of sinker bars 9 of a selected total weight to insuresufficient pressure for cutting, a battery 13, a drill motor 57, chuck58, a flexible drill shaft 59 and a cutter 61. The sinker bars 9,battery 13 and drill motor 57 are threaded into each other and the totalapparatus 12 is vertically supported from the surface for raising andlowering by a high strength stranded wire cable 8 as known in the art.The down hole housing of the drill motor has a self aligning surface,such as used on a universal down hole orientation sub known in the art,to self align the drill apparatus 12 with anti spin lugs 16 fixed intothe inner wall of the channel 53 to prevent the apparatus 12 fromrotating. The chuck 58 is threaded onto a shaft 62 of the drill motor57. The flexible drill shaft 59 is silver soldered or otherwise fixed tothe base of the chuck 58. A ramp 14 with a cam surface 54 is welded intoa slot in the channel 53 of the fixed section wall on which a mechanicalswitch 15 rides to turn the drill motor 57 on. A proximity sensor 50 ina inner guide housing 64 senses the presence of the chuck 58; a signalfrom the sensor is transmitted in a multi-conductor cable. Themulti-conductor cable 17 that conducts signals for controlling therotation of the working section 11 and indicating it's angular positionto the operator on the surface via a gyro 36. This cable is banded tothe exterior of the wall 52 of the drill string from the shoe to thesurface. This is to keep it from snagging on the inside of the wellcasing 20 and becoming damaged while tripping in or out of the hole, asshown in FIG. 3.

The fixed inner guide housing 64 threaded into the down hole end of thefixed section 10 provides a shoulder 65 onto which a cylindrical end cap18, into which the rotating section 11 is threaded, sits supported byoil filled thrust bearings 19 that allow the rotating section 11 to turnwithin the well casing 20.

The rotating section 11 comprises a cylindrical cutter support body 23,a cylindrical motor housing 24, a cylindrical battery/gyroscope housing25, and a metal shoe guide 37. A ring gear 21, detailed in FIG. 4, iswelded to or otherwise fixed to the base of the inner guide housing 64to convert the turning of a transfer bar or drive shaft 22 into rotationof this section 11 in respect to the upper fixed section 10. The innerguide housing 64 also provides an annular clearance to allow freerotation of the flexible drill shaft chuck 58 that is threaded onto thedrill motor shaft 62.

A rotating vertical sleeve 26 sealed by an o-ring 27 is recessed in acounter bore in the inner guide housing 64. The sleeve 26 passes throughthe center of the ring gear 21 and is pressed or otherwise fixed intothe cylindrical cutter support body 23. The body. 23 is threaded into orotherwise fixed to the cylindrical end cap 18. At it's lower end, thebody 23 is threaded into the cylindrical motor housing 24. The rotatingsleeve 26 guides the hole cutter 61 and the flexible drill shaft 59 intoan elbow-shaped channel 29, of circular cross-section, formed in thecylindrical cutter support body 23, that changes the direction from avertical entry into a horizontal exit. A hardened bushing 28, in thecutter support body 23 works as a bearing to support the hole cutter 61for rotation and guides the hole cutter 61 in a radial direction.

Various sized centralizing rings 60 and modified bushings 128, shown inFIG. 5, may be used so that the same shoe assembly 5 can be used incasings of different inside diameters. These centralizing rings 60 arescrewed, welded, bolted or otherwise fixed at selected locations on theoutside of the shoe assembly 5. The centralizing ring 60 should benotched, channeled or shaped like a star so only a few points touch thecasing, to allow for the free flow of fluid, gas and fines past the shoeand up and down the inside of the well casing. This design also aids inthe insertion and withdrawal of the shoe from the casing acting as acentralizing guide within the casing walls 20. Alternatively, thebushing 128 can be integral with a centralizing ring.

While the preferred hole cutter 61 is a hole saw, other cutters such asa milling cutter or other cutters known in the art may be used. Thepreferred cutter 61 comprises a hollow cylindrical body with a solidbase at it's proximal end and cutting teeth or abrading elements knownin the art, at the terminal end. A magnet may be located inside thehollow body and attached to the base to retain one or more couponsremoved from the casing 20 when a hole has been completed.Alternatively, the coupon or disc may be left in the formation andsubsequently pushed out of the path of the boring nozzle by the highpressure water.

It has been found that surprisingly good results have been achieved inthis application by using a standard hole saw as compared toconventional milling cutters. It is believed that this excellentperformance comes from the ability of the hole saw to cut a relativelylarge hole while only removing a proportionally small amount ofmaterial.

The multi-conductor cable 17 extends down through a slot 31 milled intothe walls of the rotating section 11. The multi-conductor cable 11 leadsto and is connected through grommets 32 to a bi-directional, variablespeed DC motor 30 in the motor housing 24. The DC motor 30, which iscontrolled by an operator on the surface through the multi-conductorcable 17, and vertically stabilized by security plugs 33 to keep themotor from spinning within the motor housing 24. This DC motor rotatesthe vertical transfer bar or drive shaft 22 extending upward, through aradial roller bearing 34 at each end of the shaft to aid in support androtation, to the ring gear 21, to turn the rotating section 11.

The multi-conductor cable 17 continues down through the milled slot 31in the cylindrical battery/gyroscope compartment 25 to both the batterypack 35 and a gyroscope 36 which are secured within the compartment 25.The DC battery pack 35 preferably comprises lithium batteries or otherpower supplies known in the art. The lithium batteries 35 provide powerto the DC motor 30 and to the gyroscope 36.

The gyroscope 36 may be an inertial or rate type gyroscope or any othertype of gyroscope known in the art. The gyroscope 36, fixed relative tothe rotating section 11 and specifically aligned to the exit hole of thecutter support body 23, communicates the precise direction in degrees ofthe position of the rotating section to the operator on the surface viathe multiconductor cable 17. Alternatively, this data can be relayed bywireless transmissions to allow the operator to operate the motor 30 inorder to turn the rotating section 11 to the desired position to cut ahole in the well casing 20, or to a previously cut hole-allowing thehigh pressure water hose and jet blasting nozzle to begin the boringprocess (not shown). In the absence of the preferable gyroscope 36,other methods, known in the art, for indicating the angular position ofthe rotating section 11 can be used. This will provide a starting pointand will be used to position the rotating section 11 for initial andsequential hole cutting and boring.

A beveled cylindrical metal shoe guide 37 caps the bottom of therotating section 11 for ease in lowering the entire shoe assembly 5through the well casing 20 to the desired depth.

A tail pipe 38, shown in phantom, may carry a gamma ray sensor or othertype of logging tool known in the art, and can be used to determine thelocation of a hydrocarbon payzone or multiple payzones. This loggingtool may be screwed into or otherwise attached to the shoe guide 37. Apacker 39, shown in phantom, may be attached to the tailpipe 38. Thepacker 39 as known in the art, preferably made of inflatable rubber, isconfigured in such a way that when it is expanded there are one or morechannels, notches or passageways to allow the free flow of fluid, gasand fines up and down the casing 20. When expanded, the packer 39stabilizes the position of the shoe assembly 5 restricting its abilityto move up or down the well bore thus reducing a potential problem ofbeing unable to reenter holes in the side of the casing.

In operation, when the well casing 20 is clear of all pumping, datacollecting or other working or instrumentation fixtures, the entire shoeassembly 5 is threaded into the down-hole end of the upset tubing 52 orany other means by which to transport the entire assembly 5 to thedesired depth within the well casing 20.

The technicians on the surface employ the high strength wire cable 8 tolower the drilling apparatus 12 down the inside of the upset tubing 52into the fixed section of the shoe assembly 10. The design of the drillmotor housing will ensure that the drill apparatus 12 will properlyalign itself and seat into the anti-spin lugs 16 in the fixed sectioncentral channel 53. Sensors can be installed into the shoe assembly sothat lights or other methods of indication on or at the control console,usually inside a truck, could provide a variety of information to theoperator.

Once the shoe assembly 5 is at the desired depth, the operator thenrotates the lower portion of the shoe by activating a rheostat or othercontrolling device located at the surface, and monitors a readout as tothe shoe's direction via the signals provided by the multi-conductor 17.This engages the battery 35, bi-directional motor 30, and gyroscope 36assembly by which the operator can manipulate the direction of the shoeto the desired direction or heading based on customer needs.

Technicians on the surface lower the drilling apparatus 5 so that themechanical power on switch 15 turns on the drill motor 57 at the properrate, turning the flexible drill shaft 59 and cutter 61. As the serratededge of the cutter 61 contacts the wall of the well casing 20, it beginsto form a groove in the casing 20. The selected mass of weight of thesinker bars 9 provide the appropriate thrust to the cutter. The groovedeepens until a disc or coupon is cut out of the casing wall. Theproximity sensor 50 senses the presence of the chuck 58 in the annularclearance in the inner guide housing 64, and indicates to the operatorthat the hole has been completed.

Once the operator has cut the initial hole he pulls the drillingapparatus up the hole approximately 20 feet to ensure that the flexiblecable is not obstructing the shoes ability to be turned to the nextdirection, he again uses the data provided from gyroscope 36 in thebattery/gyroscope compartment 25 and sends a signal to thebi-directional, variable speed DC motor 30 to turn the rotating section11 a specified number of degrees to cut the next hole. This processcontinues at that same desired depth until all the desired holes are cutin the well casing 20. Preferably, several sequential holes are cut atthe same depth before bringing the drill apparatus 12 to the surface.

Once the desired number of holes are cut in the well casing 20 at thedesired depth and the drilling apparatus has been removed, the processof boring into the hydrocarbon payzones at that same depth may begin.

The technicians on the surface connect a high pressure jet nozzle knownin the art (not shown), to the discharge end of a high pressure hose(not shown), which is connected to a flexible coil tubing, and begin tolower the nozzle down the upset tubing 52 and into the shoe assembly 5.Once the nozzle is seated in the elbow-shaped channel 29 in the cuttersupport body 23, the suction connection of the hose is connected to thedischarge connection of a very high pressure pump (not shown). The veryhigh pressure pump will be of a quality and performance acceptable inthe art. The pump is then connected to an acceptable water source;usually a mobile water truck (not shown).

The technicians then advise the operator at the control console thatthey are ready to begin the boring process. The operator, using theinformation provided from the gyroscope 36, ensures that the cuttersupport body 23 is aligned with the desired hole in the well casing andadvises the technicians to begin the boring process.

The technicians turn on the pump, open the pump suction valve and thehigh pressure water in the hose forces the nozzle through theelbow-shaped channel 29 and the hole in the casing and into thehydrocarbon payzone (not shown). The design of the jet nozzle housing,as known it the art, provides for both a penetrating stream of highpressure water to penetrate into the zone, and small propelling waterjet nozzles located peripherally on the back of the nozzle to propel thenozzle into the zone. The technicians on the surface monitor the lengthof hose moving into the upset tubing 52 and turn the water off andretract the nozzle back into the elbow-shaped channel 29 when thedesired length of penetration has been achieved.

With information provided by the gyroscope 36, the operator, at thecontrol console, now rotates the shoe assembly to the next hole in lineand the boring process can be repeated again. Once the boring processhas been completed at a specific depth and the boring nozzle retrievedto the surface, the upset tubing 52 and shoe assembly 5 may becompletely removed from the well casing, or alternatively raised orlowered to another depth to begin the process once again.

It is contemplated that the invention can be practiced with an assemblylike that described above, but without a bi-directional variable speedDC motor 30, drive shaft 22, ring gear 21 and related components thatenable the rotating section 11 to rotate in respect to the fixed section10. In that case the shoe assembly 5 would comprise only fixedsub-assemblies. In such a case the entire assembly would be rotated byphysically turning the upset tubing 52 from the surface. The dataprovided from the gyroscope 36 would be used to similarly locate thehole cutting locations and boring positions as described. While anelectric motor is preferred for operating the cutter 61, a mud motor,known in the art, can alternatively be used. The mud motor is driven byfluid pumped through coil tubing connected to it from the surface.

Apart from the specific disclosures made here, data and information fromthe proximity sensor 50, gyroscope 36, gamma ray sensor, sonar or othersensors that may be used, may be transmitted to the operator on thesurface by optical fiber, electrical conduit, sound or pressure waves asknown in the art. Similarly, both the drill motor 57 and thebi-directional, variable speed DC motor 30 can be driven directly fromthe surface through appropriate power cables.

It should be evident that this disclosure is by way of example and thatvarious changes may be made by adding, modifying or eliminating detailswithout departing from the fair scope of the teaching contained in thisdisclosure. The invention is therefore not limited to particular detailsof this disclosure except to the extent that the following claims arenecessarily so limited.

1-25. (canceled)
 26. Apparatus for drilling in a well, said apparatuscomprising a shoe assembly, a hole saw, an electric motor operativelycoupled to said hole saw, and a gyroscope, said shoe assembly beingadapted to be lowered into a casing of the well and to direct said holesaw in a predetermined direction at a depth at which a hole or holes areto be cut in a casing wall of said well, said shoe assembly having alongitudinal pathway adapted to receive said hole saw therein, and alateral pathway oriented at an angle relative to, and in fluidcommunication with, said longitudinal pathway, said lateral pathwaybeing adapted to receive said hole saw from said longitudinal pathwayand to direct said hole saw against said casing wall, said gyroscopebeing adapted to transmit a signal to indicate an angular location ofsaid hole saw within said well casing.
 27. Apparatus according to claim26, said hole saw comprising a hollow cylindrical body having, at aserrated end thereof, a serrated edge comprising a plurality of cuttingteeth.
 28. Apparatus according to claim 26, said hole saw furthercomprising a solid base at a proximal end thereof opposite said serratedend.
 29. Apparatus according to claim 26, said casing having an innersurface and an outer surface, said cutting teeth at said serrated edgebeing effective to cut a circular groove in said inner surface of saidcasing during a drilling operation.
 30. Apparatus according to claim 29,said cutting teeth being further effective to cut a coupon out of saidwell casing during a drilling operation.
 31. Apparatus according toclaim 26, said shoe assembly further comprising a support body forsupporting said hole saw adjacent an angular location at which it isdesired to form a hole in said well casing, said gyroscope being fixedrelative to said support body, and being adapted to transmit a signal toindicate the angular location of the support body.
 32. Apparatusaccording to claim 27, said hole saw further comprising an arborextending at least partly forward of said serrated edge of saidcylindrical body.